One-piece pressure container

ABSTRACT

A pressure container made of aluminum, for example, is disclosed and includes a generally cylindrical body and a self-standing integral bottom which has a downwardly extending peripheral skirt portion. The bottom of the container has an inside radius of about R1 and an exterior configuration which, in vertical crosssection along a diameter line includes: I. A DISC-LIKE, CIRCULAR CENTRAL PORTION; II. A CONCENTRIC UPWARDLY CURVED PORTION WHICH IS CONTIGUOUS WITH THE CENTRAL PORTION AND HAS A RADIUS OF ABOUT 0.22 R1; iii. a concentric downwardly curved portion contiguous with the skirt portion and having a radius of about 0.19 R1; and IV. A GENERALLY FLAT CONCENTRIC PORTION CONTIGUOUS WITH AND BETWEEN THE CURVED PORTIONS. The thinnest portion of the bottom is in the upwardly curved portion and is not less than about 1.5, preferably 2 times the wall thickness of the cylindrical body.

United States Patent [191 Avant et al.

[ 1 ONE-PIECE PRESSURE CONTAINER [75] Inventors: Richard H. Avant,Rochester; Peter R. Webster, Greece, both of NY.

[73] Assignee: BernzOmatic Corporation,

Rochester, NY.

[22] Filed: May 10,l974

21 Appl. No.: 468,962

[52] US. Cl. 220/3; 220/66; 220/70 [51] TM. CI. ..F17c 1/14; B65d l/16;B65d H42 [58] Field of Search 220/3, 66, 67, 70, 73, 220/74; 215/1 R, 1C

[56] References Cited UNITED STATES PATENTS 79,692 7/1868 Scantlin etal. 220/70 7 651,884 6/1900 Platz 220/70 1,878,709 9/1932 Kerr.....220/73 X 2,541,065 2/1951 Jabour 220/3 3,038,627 6/1962 Daley 220/33,115,281 12/1963 vSomme.... 220/70 X 3,279,640 10/1966 Dodson 220/67 X3,409,167 11/1968 Blanchard... 220/66 3,434,626 3/1969 Kinslow, Jr.220/66 FOREIGN PATENTS OR APPLICATIONS 11,593 7/1889 United Kingdom220/70 432,718 8/1935 United Kingdom.... 220/3 1,344,861 10/1963 France220/3 Sweden 220/70 June 17, 1975 Primary Examiner-William 1. Price 1Assistant Examiner-Stephen Marcus I Attorney, Agent, or Firm-Burge ss,Dinklage Sprung [5 7] ABSTRACT A pressure container made of aluminum,for example, is disclosed and includes a generally cylindrical body anda self-standing integral bottom which has a down The thinnest portion ofthe bottom is in the upwardly curved portion and is not less than about1.5, preferably 2 times the wall thickness of the cylindrical body.

8 Claims, 2 Drawing Figures portion PAIENTEDJUN 11 ms :19; 8 89,8 35

FIG. I.

PRIOR RT ONE-PIECE PRESSURE CONTAINER BACKGROUND This invention relatesto a one-piece pressure container preferably made of aluminum which isespecially suited for use as a fire extinguisher where the contents areunder relatively high pressure. More particularly, this inventionrelates to a one-piece aluminum pressure container having an integralself-standing bottom which meets contemporary safety standards.

Impact extruded aluminum containers have been used for fireextinguishers and the like where the contents are under pressure. Atfirst, such containers were formed with a domed bottom, and, if thecontainer was to be self-standing, a separate plastic or metal bottomcap had to be attached over the domed bottom. It was then proposed toreverse the bottom of the container and impact extrude the containerwith an integral skirt portion. However, because of certain unique coldflow characteristics of aluminum under high impact, it was found thatreversing the bottom to form a skirt portion resulted in the formationofa concentric, unfused seam which reached depths as great as about 0.14inch. This created an undesirable structural defect which resulted inthe skirt portion falling off when the container was subjected to highimpact such as by dropping a loaded or charged fire extinguisher onto ahard surface.

The present invention overcomes this structural problem and provides aself-standing integral bottom structure for aluminum pressure containersthat can be formed as a part of the container by impact extrusion in onestep. The pressure container of the invention is structurally sound andmeets all requirements of Underwriters Laboratories, Inc. (UL) for fireextinguishers and the like.

SUMMARY The pressure container of the invention comprises a generallycylindrical body and a self-standing integral bottom having a peripheralskirt portion, said bottom having an inside radius of about R and anexterior configuration which, in vertical cross-section along a diameterline, includes:

i. a disc-like, circular central portion;

ii. a concentric upwardly curved portion contiguous with the centralportion and having a radius of about 0.22 R;

iii. a concentric downwardly curved portion contiguous with the skirtportion and having a radius of about 0.19 R; and

iv. a generally flat concentric portion contiguous with and between thecurved portions.

The thinnest portion of the bottom is in the upwardly curved portion andis not less than about 1.5, preferably about 2 times the wall thicknessof the cylindrical body.

With a bottom structure as described, it is now possible to form aone-piece aluminum pressure container in one step having an integralbottom with a concentric seam no greater than about 0.03 to about 0.06inch deep, preferably no greater than about 0.04 inch deep.

DESCRIPTION OF THE DRAWING The present invention will be more fullyunderstood from the following description taken in conjunction with theaccompanying drawing wherein:

FIG. 1 is a vertical cross-sectional view, partly broken away, along thelongitudinal axis of the pressure container of the present invention;and

FIG. 2 is vertical cross-sectional view, partly broken away, of anintegral bottom structure according to the prior art.

DESCRIPTION Referring now to the drawing and in particular FIG. 1, thepressure container of the invention which is preferably formed fromaluminum is shown to include a generally cylindrical body 10 and aself-standing integral bottom which is generally identified by referencenumeral 12. An otherwise conventional threaded neck portion 14 is formedat the upper portion of the container as shown. The upper or neckportion of the container can have any configuration, depending on theuse intended for the container and the neck structure shown in thedrawing is only for purposes of illustration and is not intended to beotherwise limiting.

The integral bottom 12 is shown to have an inside radius R and anexterior configuration which, in vertical cross-section along a diameterline includes, central portion 20 having a diameter d, upwardly curvedportion 22 which is concentric with and contiguous to the centralportion 20 and having a radius R equal to about 0.22 R, a concentric,downwardly curved portion 26 joined to or contiguous with the skirtportion 28 and having a radius R equal to about 0.19 R and a generallyflat concentric portion 24 which is contiguous with and between thecurved portions 22 and 26.

The thinnest portion of the bottom 12 is positioned or located in theupwardly curved portion 22 and is identified in the drawing by referencecharacter e. The thickness e is not less than about 1.5, preferably 2times the wall thickness f of the cylindrical body 10.

To prevent rocking and to insure upright stability of the container, thecentral portion 20 lies in a horizontal plane which is higher than thehorizontal plane of the lower end of the skirt portion 28.

In a further preferred embodiment the central portion 20 has a diameterd as shown and the diameter of the central 20, together with theupwardly curved portion 22 is about 1.5 d. This is shown in the drawingby the diameter line c. The diameter of the central portion d, togetherwith the upwardly curved portion 22 and the flat portion 24 ispreferably about 2 d. This is shown in the drawing by diameter line a.The width b of the flat portion 24 will vary, depending on the size ofthe container, whereas the relationship between the radii R, R and Rwill remain fairly constant as described above.

The lower end of the skirt portion 28 is preferably curved and has aminimum radius R, which is equal to about 0.045 R.

FIG. 2 of the drawing depicts a concentric seam 18 which radiates fromthe curved portion 16 of the bottom of the prior art container. Thisseam 18 is formed due to certain unique cold flow characteristics ofaluminum under high impact and reaches depths as great as about 0.14inch. The bottom structure of the invention as shown in FIG. 1practically eliminates this undesirable unfused seam 18 and provides asmooth transformation from the'central portion 20 up through the portion22, across the portion 24, down through the portion 26 and finally downto the skirt 28. In practice it has been found that a certain residualseam or surface roughening will occur in the downwardly curved portion26. However, this does not detract from the structural integrity of thecontainer of'the invention" and it has been found that a concentric seam30, as shown in FIG. 1 in the downwardly curved portion 26, can betolerated with depths between about 0.03 to about 0.06 inch andpreferably no greater than 0.04 inch deep.

When an aluminum slug is inserted into the cavity of an impact extrusiondie, it is believed that a lower portion of the slug cold flows alongthe bottom of the die conforming to the configuration thereof, while anupper zone flows outwardly to the side of the die cavity. With a sharpradius such as shown by reference numeral 16 in FIG. 2, the aluminum inthe lower zone is believed to flow over the radius 16 and into thedownwardly extending skirt portion faster than aluminum flowing from theupper portion of the slug. This is thought to account for theundesirable formation of an unfused seam 18 which can cause the skirtportion to fall off upon impact. In the present invention, the upwardlycurved portion 22 containing the minimum bottom thickness e is believedto function as a gate area for the cold flowing aluminum and the flatportion 24, following the upwardly curved portion 22, is believed tofunction as a pressure retard zone which compensates for the differencesin cold flow characteristics of the aluminum. In other words, the flatportion 24 acts as a pressure retard zone in cooperation with the gatee, which cause the aluminum to cold flow at substantially the same ratesand thereby form the downwardly curved portion 26 and the downwardlyextending skirt portion 28 without the formation of an undesirableunfused seam 18, such as shown in FIG. 2 of the drawing.

What is claimed is:

1. Pressure container comprising a generally cylindrical body and aself-standing integral bottom having a peripheral skirt portion, saidbottom having an inside radius of about R and an exterior configurationwhich,

in vertical cross-section along a diameter line, includes: i. adisc-like, circular central portion;

ii. a concentric upwardly curved portion contiguous with said centralportion and having a radius of about 0.22 R;

iii. a concentric downwardly curved portion contiguous with the skirtportion and having a radius of about 0.19 R; and

iv. a generally flat concentric portion contiguous with and between thecurved portions.

2. Pressure container of claim 1 wherein the thinnest portion of saidbottom is in the upwardly curved portion and is not less than 1.5 timesthe wall thickness of the cylindrical body.

3. Pressure container of claim 1 wherein said central portion lies in aplane higher than the horizontal plane of the lower end of the skirtportion.

4. Pressure container of claim 1 wherein said central portion has adiameter d and the diameter of the central portion, together with theconcentric upwardly curved portion is about 1.5 d.

5. Pressure container of claim 1 wherein said central portion has adiameter d and the diameter of said central portion, together with theconcentric upwardly curved portion and the concentric generally flatportion is about 2 d.

6. Pressure container of claim 2 wherein said thinnest portion is notless than about 2 times the wall thickness of the cylindrical body.

7. Pressure container of claim 1 wherein the lower end of the skirtportion is curved and has a minimum radius of about 0.045 R.

8. Pressure container of claim 1 wherein said downwardly curved portionhas a concentric circular seam with a depth in the range of about 0.03to about 0.06

1. Pressure container comprising a generally cylindrical body and aself-standing integral bottom having a peripheral skirt portion, saidbottom having an inside radius of about R1 and an exterior configurationwhich, in vertical cross-section along a diameter line, includes: i. adisc-like, circular central portion; ii. a concentric upwardly curvedportion contiguous with said central portion and having a radius ofabout 0.22 R1; iii. a concentric downwardly curved portion contiguouswith the skirt portion and having a radius of about 0.19 R1; and iv. agenerally flat concentric portion contiguous with and between the curvedportions.
 2. Pressure container of claim 1 wherein the thinnest portionof said bottom is in the upwardly curved portion and is not less than1.5 times the wall thickness of the cylindrical body.
 3. Pressurecontainer of claim 1 wherein said central portion lies in a plane higherthan the horizontal plane of the lower end of the skirt portion. 4.Pressure container of claim 1 wherein said central portion has adiameter d and the diameter of the central portion, together with theconcentric upwardly curved portion is about 1.5 d.
 5. Pressure containerof claim 1 wherein said central portion has a diameter d and thediameter of said central portion, together with the concentric upwardlycurved portion and the concentric generally flat portion is about 2 d.6. Pressure container of claim 2 wherein said thinnest portion is notless than about 2 times the wall thickness of the cylindrical body. 7.Pressure container of claim 1 wherein The lower end of the skirt portionis curved and has a minimum radius of about 0.045 R1.
 8. Pressurecontainer of claim 1 wherein said downwardly curved portion has aconcentric circular seam with a depth in the range of about 0.03 toabout 0.06 inch.